JPH0645902B2 - Post-treatment method for plated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to post-treatment of a steel plate for soldering, spread of solder, solder strength (hereinafter abbreviated as solderability), corrosion resistance, workability and aging property. Excellent post-treatment method.

[Conventional technology]

In recent years, Sn-plated steel sheets and Pb-Sn sheets have been used as solderable steel sheets.
Galvanized steel sheet, Cu-plated steel sheet and Zn-plated steel sheet are used. These plated steel sheets change their appearance (color) and rust when exposed to the environment in which they are used after each plating. Therefore, in order to improve the corrosion resistance, a chemical conversion treatment such as a chromate treatment or a phosphate treatment, or a temporary rust preventive agent is applied. In the case of chromate treatment, Cr needs to be 0.1 mg / dm ² or more to improve the corrosion resistance. However, when chromate treatment is applied, the solderability is significantly reduced, and when it is 0.05 mg / dm ² or more, it is corrosive. This is a practical problem unless a strong and strong flux of is used during soldering. If a corrosive flux is used, the environment during soldering will be adversely affected and the corrosion resistance of the solder part will be significantly reduced. Therefore, Cr is 0.05 mg / d
Since it is kept below m ² , sufficient corrosion resistance cannot be obtained.
In addition, the method of applying the temporary rust preventive agent may reduce the solderability as in the case of the chromate treatment. Moreover, the corrosion resistance after soldering is extremely poor.

[Problems to be solved by the invention]

As described above, in order to obtain a soldering steel sheet having excellent characteristics, it is necessary to carry out a post-treatment after plating to improve the corrosion resistance without impairing the solderability of the plated steel sheet. However, with known post-treatment methods, improvement in solderability and corrosion resistance tend to contradict each other, so it is difficult to obtain a steel sheet excellent in corrosion resistance and solderability. This tendency is remarkable when the plated steel sheet is aged. In other words, it is considered that the oxide film on the plating surface grows over time and the wetting of the solder is deteriorated.

Therefore, it is necessary to improve the post-treatment after plating.

[Means for solving problems]

The post-treatment after plating according to the present invention is carried out by adding 5 to 200 g of water-soluble or water-dispersible phosphate ester salt, or 0.01 to 3 g of Cr ⁶⁺ ion, and 10 to 10 g of organic amine soap.
PH 3 to 10 with addition of 0g / single or mixed
It is characterized in that the plated steel sheet is treated with the treatment liquid of (1) to a dry thickness of 0.01 to 2 μm.

Hereinafter, the present invention will be described in detail.

The water-soluble or water-dispersible phosphoric acid ester salt, which is the main component of the present invention, is in the form of a monobasic or dibasic acid having one or two alkyl groups, or a soap with an organic amine. Is included. Further, those having a large alkyl group and insoluble in water can be used by enhancing the hydrophilicity by forming an alkali salt or adding ethylene oxide or the like.

When the above-mentioned concentration is below the proper concentration, the effect of solderability is not recognized. When the concentration is higher than the proper concentration, the effect of solderability is saturated and the drying becomes poor.

To stabilize the treatment liquid or to improve the corrosion resistance and scratch resistance of the plated steel sheet, Cr ⁶⁺ or organic amine soap, alone or in a mixture, is added.
If the Cr ⁶⁺ ion ^content is 3 g / or more, the ^{solderability} is extremely deteriorated, which is not preferable. Organic amine soaps include dodecyl amine, oleoyl imidazoline, aminopropyl tallow amine, and rosin amine, and the amine can be used after salt formation with carboxylic acid. The concentration is 100g /
If it is more than the above value, the corrosion resistance is effective, but the solderability is deteriorated, which is not preferable.

Other known water-soluble or water-dispersible rust preventives may be added. However, in this case, it is necessary to pay attention to the amount of addition, because there are some that deteriorate the solderability. For example, the addition of acrylic emulsion improves the scratch resistance but decreases the solderability.

The pH of the treatment liquid is suitably in the range of 3-10. When it is 3 or less, the stability of the treatment liquid is poor, and when it is 10 or more, the drying property of the treatment film is poor.

The temperature of the treatment liquid is not particularly limited, but when it exceeds 80 ° C, it may gel and deteriorate the stability of the treatment liquid.
~ 40 ℃ is economical.

The coating method is not limited to roll coating, knife coating, roll squeezing after dipping, or air knife squeezing.

Drying is not particularly problematic if it is not tacky to the touch, but residual water is not preferred because it causes rusting over time.

A suitable dry thickness of the post-treatment film is 0.01 to 2 μm. 0.
If it is less than 01 μm, the effect of characteristics cannot be recognized. 2 μm
As described above, the corrosion resistance tends to be improved, but the solderability is saturated and the workability is deteriorated, which is not preferable.

[Action]

In the post-treatment of the present invention, a treatment liquid containing a phosphoric acid ester as a main component, or Cr ⁶⁺ ions, and a rust preventive added to the Sn-plated steel sheet, Pb-Sn-plated steel sheet, Cu-plated steel sheet or Zn-plated steel sheet surface. When applied, not only the solderability but also the corrosion resistance is significantly improved. In addition, the plated steel sheet has excellent solderability and corrosion resistance after aging. The applied steel plate is not limited to the above-mentioned plated steel plate.

Although the reason why the characteristics are improved is not clear, the formation of oxides, hydroxides and carbonates formed on the plated surface is suppressed by the post-treatment of the present invention, and moreover, it is formed over time of the plated steel sheet. In addition, since the coating film of the present invention dissolves and partially reduces the metal compound on the plating surface by heating during soldering, the solder wets,
It is considered that diffusion is promoted and solderability is improved. Further, it is considered that the above-mentioned phenomenon improves the corrosion resistance because the coating film of the present invention uniformly coats the plating surface.

The present invention has been made based on such knowledge, and by uniformly coating the surface of a plated steel sheet with the treatment liquid of the present invention, it is possible to continuously produce a plated steel sheet for solder excellent in solderability and corrosion resistance. Is characterized by.

〔Example〕

 Hereinafter, the effects of the present invention will be described with reference to examples.

Example 1 A cold-rolled steel sheet having a thickness of 0.5 mm was subjected to conventional degreasing and pickling pretreatments as a plating original sheet, and electrogalvanized so that the plating amount was 5 g / m ² immediately after washing with a sulfuric acid bath. Then, the process of the present invention was performed. That is, a treatment solution was prepared so that monobasic phosphate ester (manufactured by Kyoeisha Oil & Fat Co., Ltd.) was adjusted to 0.01 g / as Cr ⁶⁺ ions with CrO ₃ and the dry thickness of the treatment solution was 2.0 μm. Coating by dipping method so that
A test piece was prepared by drying at 0 ° C.

In the processing of the invention of the present application in Examples 2 to 6, test pieces were prepared according to Example 1.

Comparative Example 1 A plating base plate was pretreated in the same manner as in Example 1, electrogalvanized in a sulfuric acid bath to a plating amount of 5 g / m ² , and subjected to a known chromate treatment. In other words, / chromic anhydride 20g, with sulfuric acid 0.05 g / bath composition, it is immersed for 1 second in a bath temperature of 30 ° C., 0.05 mg / dm ² Chromate amount as Cr
The sample was treated so that

In Comparative Examples 2 to 4 as well, plating was performed by a known method, and then post-treatment was performed. Comparative Example 5 is a test piece having only plating.

Next, the preparation of the test piece is summarized in Table 1, and the evaluation of the characteristics is summarized in Table 2.

As shown in Examples 1 to 6 in Table 2, the treated film of the present invention showed excellent effects in corrosion resistance, solderability and aging. Comparative Example 5 is the one in which no post-treatment is applied, and Comparative Example 1
~ 4 is commonly used Characteristic evaluation Spread of solder: 50mm × 50mm on the solder bath kept at 250 ℃
The test piece of No. 3 was held stationary, and a solder (JIS Z 3283, RH50) with a goby folded with a weight of 0.4 g was placed on it, and the solder spread area after 5, 10, and 15 seconds was measured and evaluated.

○: Spreading area 200 mm ² or more ×: 50 mm ² or less Solder strength; 0.18 mmφ fine copper wire 20 cores are placed on the test piece and soldered with a soldering iron (RH50) to form a copper wire. The test piece was forcibly broken by pulling in parallel with the test piece in the opposite direction, and the state was evaluated. ○: No destruction
×: Complete destruction Corrosion resistance: A salt spray test according to JIS Z 2371 was performed for 2 cycles (1 cycle: spraying for 8 hours, stopping for 16 hours), and the presence or absence of red rust was evaluated.

○: No red rust ×: Full red rust processing method: Erichsen overhang (Er = 7mm) and DuPont impact (1/2 ″ × 1kg × 30cm) were performed, and the adhesion of plating processing was evaluated with cellophane tape. Change over time: Appearance (discoloration) was observed after 1,000 hours at constant temperature and humidity (60 ° C, RH 95% or higher), and corrosion resistance and solderability were evaluated by the above test. Chromate treatment and phosphoric acid treatment were applied as chemical conversion treatments, but those showing an effect on corrosion resistance showed poor solderability due to poor solder wetting, and the surface color tone changed over time. The corrosion resistance and the corrosion resistance tended to decrease.

〔The invention's effect〕

As shown in Examples 1 to 6 in Tables 1 and 2, the method of the present invention enabled the production of plated steel sheets having excellent corrosion resistance, solderability, workability, and aging.

Claims (1)

[Claims] 1. A post-treatment of a plated steel sheet for solder, which comprises 5 to 200 g of a water-soluble or water-dispersible phosphate ester salt
Alternatively, 0.01 to 3 g of Cr ⁶⁺ ions /, or 10 to 100 g / of organic amine soap alone or a mixture of pH 3 to 10 is added to the treatment liquid so that the dry thickness becomes 0.01 to 2 μm. A post-treatment method featuring plated steel sheets for soldering.